MXS-228: Include file name and line numbers

This change does not log the file name and line numbers,
but the function name. Together with the commit information
that is logged in conjunction with a crash and that MaxScale
can tell, when invoked, that is enough to be able to pinpoint
the location where a logging was made. Furthermore, that is
a lot less intrusive and less confusing for an
end-user than filename + line.

This is just a temporary workaround; the logging mechanism
needs to get an overhaul:

- Separate severity and logging target.
- Take syslog severities into use.
- Simplify what needs to be done by developer.
- etc.

log_manager/log_manager.h

@@ -118,11 +118,15 @@ void skygw_logmanager_exit(void);
  * free private write buffer list
  */
 void skygw_log_done(void);
-int  skygw_log_write(logfile_id_t id, const char* format, ...);
+int  skygw_log_write_context(logfile_id_t id,
+                             const char* file, int line, const char* function,
+                             const char* format, ...);
 int  skygw_log_flush(logfile_id_t id);
 void skygw_log_sync_all(void);
 int  skygw_log_rotate(logfile_id_t id);
-int  skygw_log_write_flush(logfile_id_t id, const char* format, ...);
+int  skygw_log_write_context_flush(logfile_id_t id,
+                                   const char* file, int line, const char* function,
+                                   const char* format, ...);
 int  skygw_log_enable(logfile_id_t id);
 int  skygw_log_disable(logfile_id_t id);
 void skygw_log_sync_all(void);
@@ -130,6 +134,12 @@ void skygw_set_highp(int);
 void logmanager_enable_syslog(int);
 void logmanager_enable_maxscalelog(int);
 
+#define skygw_log_write(id, format, ...)\
+    skygw_log_write_context(id, __FILE__, __LINE__, __FUNCTION__, format, ##__VA_ARGS__)
+
+#define skygw_log_write_flush(id, format, ...)\
+    skygw_log_write_context_flush(id, __FILE__, __LINE__, __FUNCTION__, format, ##__VA_ARGS__)
+
 EXTERN_C_BLOCK_END
 
 const char* get_trace_prefix_default(void);